Gaze behavior in stroke patients during reach and grasp tasks and the star cancellation test in stroke patients

After stroke, patients might suffer from upper extremity weakness or hemiparesis. [1] For example, picking up a cup of coffee might be difficult. For this reason, there is worked on an arm and hand support system in the eNHANCE project. To control this system, motion intention detection by using 3D eye tracking, which does not add cognitive load, might be used. [2] To find out if this can be used to control the system, the until now unknown gaze behavior during reach and grasp tasks in stroke patients should be mapped. This is the first part of the observational research. The other part of the observational research is about Unilateral Spatial Neglect (USN), this is a condition after stroke where the patient neglects part of the visual field. A diagnostic tool for this is the star cancellation test (SCT). This is a pen and paper test where small stars in between larger stars and letters should be canceled. However, no restriction in time or head movements are used (which might be used as compensatory strategy). Therefore, there should be looked into the effect of time and head movements on the SCT and also other potential distinguishing parameters should be investigated to make diagnosis of USN by use of the SCT more sensitive.
The goal of this master thesis was to set up the measurements and to find the valuable and obtainable parameters for the whole observational study into the gaze behavior of stroke patients during reach and grasp tasks and into the potential distinguishing parameters in the SCT. After that there should be looked into the feasibility of the measurements and the analysis.
In total, 7 healthy subjects and 3 stroke patients were measured, where 2 healthy subjects and 2 patients (1 in the reach and grasp part and 1 in the SCT part) were included in the analysis of this master thesis. Gaze was tracked by using a wearable 3D eye tracker, the Tobii Pro Glasses 2 with an integrated gyroscope. The fixations were detected by using a custom eye movement velocity threshold filter in the Tobii Pro Lab software. To map the gaze behavior during reach and grasp tasks, four different personalized simulated all day life reach and grasp tasks were programmed on a touchscreen. These tasks are a reach and touch, a reach and lift, a reach and replace and a bimanual task. Touchscreen compatible objects were built and used in the reach and grasp tasks. The data of the tasks executed three times with the dominant hand in the healthy subjects group and three times with the hand of the affected side in the patient group was analyzed. The SCT was executed once without and once with head fixation, by using a chin rest. A head movement detection script was written to find the head movements from the gyroscope data. Parameters which are valuable to the observational research and which should be ob- tainable from the eye tracker, the touchscreen and the SCT were listed for the reach and grasp tasks and the SCT.
Most of the parameters listed were obtainable except for the parameters which need the fixations on the areas of interest data. These parameters were replaced by others which still give information about the gaze on the areas of interest by using the raw gaze points instead of the fixations. All reach and grasp tasks were executable for the healthy subjects and the patient. The programmed tasks worked as expected and promising results were found. The same goes for the SCT with and without head fixation. In the results of the SCTs was found that the head fixation system does limit, but does not exclude head movements.
At this moment the study population is too small to draw solid conclusions in the whole observational study, but insight into the feasibility of the study was gained. In future research there should be looked into how to get the fixations on the areas of interest data. This will give information about if a subject took up information while looking at an area of interest. There could also be looked into how to find the fixations more validly with the wearable eye tracker. In conclusion, the measurement, which was set up, and the analysis are feasible. A lot of the parameters were obtainable, only those requiring the fixations on the areas of interest data could not be obtained. During this master thesis, the first steps were taken into the fundamental research into gaze behavior in stroke patients during reach and grasp tasks and into finding potential distinguishing parameters for USN during the SCT.